Display apparatus and method capable of rotating an image by 180 degrees

1. A graphics system for rotating an image for display from a first orientation to a second orientation comprising: a first input that receives image pixel data signals representing picture elements successively in columns across rows, and in rows across a screen; a second input that receives image pixel address signals successively identifying the row and column of corresponding pixel data signals in the first orientation; an address translation system that receives said image pixel address signals and translates them into translated address signals successively identifying the column and row of corresponding pixel data signals representing picture elements successively in rows across columns, and in columns across a screen in the second orientation, and selectively outputs one of said image pixel address signals and said translated address signals as logical address signals; refresh logic that generates screen refresh address signals; a multiplexer that receives said logical address signals and said refresh address signals, and is responsive to a select signal to select one of said address signals and pass it as a memory address signal; and a memory address arbitrator that generates said select signal.

2. A graphics system for rotating an image for display on a landscape-configured display with a landscape-oriented height (H D ) in pixel-lines and width (W D ) in pixel-lines, the graphics system comprising: an input terminal that receives a software address and corresponding pixel data; an address translation system comprising (i) configuration registers that store a flag representing orientation of a display; (ii) a translation circuit that translates the software address as a translated address according to the functions L ln (H D )/ln 2 and M ln(W D )/ln 2, wherein L specifies the number of least significant bits in the software address to copy as the most significant bits in the translated address, and M specifies the number of most significant bits in the software address to invert and then copy as the least significant bits in the translated address; and (iii) a selector that selectively outputs the software address as a logical address when the flag indicates landscape orientation, and outputs the translated address as the logical address when the flag indicates portrait orientation; and refresh address generation circuitry that generates a refresh address; and arbitration circuitry that selects one of the refresh address and the logical address as a selected address.

3. A method for rotating an image for display on a graphic display having a first orientation with a pixel height (H D ) and pixel width (W D ), to a second orientation, comprising: retrieving configuration information indicating a display orientation; generating a software address representing an image position on a display and generating corresponding pixel data; when the display orientation indicates the first orientation, selecting the software address as a logical address; and when the display orientation indicates the second orientation, translating the software address based on the functions L ln (H D )/ln 2 and M ln (W D )/ln 2, wherein L represents the number of least significant software address bits to copy as the most significant translated address bits, and M specifies the number of most significant software address bits to invert and then copy as the least significant translated address bits, and selecting the translated address as a logical address.

4. The method for rotating an image for display on a graphic display according to claim 3 wherein said first orientation is a landscape orientation and said second orientation is a portrait orientation.